Photodynamic therapy for biliary tract organ via a novel ultra-small composite optical fiberscope.

Photodynamic therapy (PDT) is a method used treat tumors via utilizing photodynamic reactions between photosensitive substances with tumor affinity and lasers. For overall bile duct cancers, PDT has been demonstrated to resolve stenosis and improve prognosis; however, when limited to intrahepatic bile duct cancers, modifications to the laser irradiation are necessary as surrounding hepatocytes incorporate a large amount of photosensitive substances. Furthermore, the intrahepatic bile duct is thin, and a guide sheath and thin fiber are necessary to transport laser irradiation probes to the target region. In the present study, a parallel-type ultra-small composite optical fiberscope (COF) with an outer diameter of 1 mm or smaller was developed to target a thin intrahepatic bile duct. PDT was performed using an animal model and talaporfin sodium (Laserphyrin), which is rapidly excreted by hepatocytes and is suitable for use with a long-wavelength laser due to its high tissue penetrating ability. The results demonstrated that Laserphyrin does not cause necrotic changes in the normal biliary tract mucosa. In addition, COF images of sufficient quality were acquired. The present results suggest that COF may be used for the treatment of deep bile duct lesions.